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| Titel |
Quantification of PM2.5 organic carbon sampling artifacts in US networks |
| VerfasserIn |
J. C. Chow, J. G. Watson, L.-W. A. Chen, J. Rice, N. H. Frank |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 12 ; Nr. 10, no. 12 (2010-06-15), S.5223-5239 |
| Datensatznummer |
250008550
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| Publikation (Nr.) |
 copernicus.org/acp-10-5223-2010.pdf |
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| Zusammenfassung |
| Field blanks (bQF) and backup filters (quartz-fiber behind quartz-fiber
filter; QBQ) have been adopted by US long-term air quality monitoring
networks to estimate PM2.5 organic carbon (OC) sampling artifacts. This
study documents bQF and QBQ carbon levels for the: 1) Interagency Monitoring of
Protected Visual Environments (IMPROVE); 2) Speciation Trends Network (STN;
part of the Chemical Speciation Network [CSN]); and 3) Southeastern Aerosol
Research and Characterization (SEARCH) networks and examines the
similarities/differences associated with network-specific sampling
protocols. A higher IMPROVE sample volume and smaller filter deposit area
results in PM2.5 areal density (μg/cm2 on filter) 3–11 times
those of STN/CSN and SEARCH samples for the same ambient PM2.5
concentrations, thus reducing the relative contribution of sampling
artifacts from passive OC adsorption. A relatively short (1–15 min)
passive exposure period of STN/CSN and SEARCH bQF OC (0.8–1 μg/cm2)
underestimates positive and negative OC artifacts resulting
from passive adsorption or evaporation of semi-volatile organic compounds on
quartz-fiber filters. This is supported by low STN/CSN and SEARCH bQF levels
and lack of temporal or spatial variability among the sites within the
networks. With a much longer period, ~7 days of ambient passive
exposure, average IMPROVE bQF and QBQ OC are comparable (2.4±0.5 and
3.1±0.8 μg/cm2, respectively) and more than twice levels
found in the STN/CSN and SEARCH networks. Sampling artifacts in STN/CSN were
estimated from collocated IMPROVE samples based on linear regression. At six
of the eight collocated sites in this study, STN/CSN bQFs underestimated OC
artifacts by 11–34%. Using a preceding organic denuder in the SEARCH
network minimized passive adsorption on QBQ, but OC on QBQ may not be
attributed entirely to the negative sampling artifact (e.g., evaporated or
volatilized OC from the front filter deposits after sample collection). |
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